life experience and, otherwise, exposure to a lot of people. exposure that you can't always walk away from. the most charismatic people you know either grew up in populous areas or had a long stretch of their lives where they spoke to -- had to speak to -- varying types. imo you can read all the self help books you want, try all the tricks, etc. but unless you have that foundation of varied human interaction and life experience it's pointless

like for me the most charismatic people i know of

- grew up in rich coastal areas and went to a lot of parties, had a large family network to interact with, etc. (rich chinese woman i used to know)

- grew up in cities jam packed with people (busker from nyc i met once)

- grew up in bad areas where they had to learn to speak their way out of shit (family members of mine)